Preliminary dough: Knead the ingredients into a smooth dough. Cover the bowl with plastic wrap and let it stand at room temperature until the next day. To be potent enough for the next step, the dough should have risen, attained a sour smell and sunk down again.
Bread dough: Mix the preliminary dough with yeast, water and salt. Knead in the two types of flour and knead in the oil last. Kneed this with your hands until it clings together and doesn’t stick to your hands.
Work the dough on and off the table until it is totally pliable.
Allow the dough to rise to three times its unleavened size on a large platter.
Pour the dough onto the table and form into bread without deflating it. You want it to retain as much of its volume as possible.
Let the loaves rise again in a leavening basket or directly on the baking sheets. You want them to double in size. If a leavening basket or container is used, slide them carefully onto greased baking sheets that have been pre-heated in the oven or on a baking stone.
Sprinkle the loaves with a thick layer of flour and place then in a 250°C oven. Toss a cup of water into the bottom of the oven and close the door quickly so the steam is retained. Bake for 20 minutes, turn down to 190°C and bake until done. The time depends on the size of the loaves.